This research project is concerned with two major subjects: One is the electrophysiological studies of the autonomic ganglia in reference to the neuronal properties, the mechanisms underlying synaptic transmission and modulation, and the electrogenesis of postsynaptic potentials. Our specific aims in this subject are: 1) Study of the facilitation and depression of ganglionic transmission in terms of the quantal release of acetylcholine from preganglionic nerve terminals. 2) Determination of the functional role of the endogenous dopamine in ganglionic transmission. 3) Investigation of the mechanism of generation of the slow i.p.s.p. and the postsynaptic hyperpolarizations induced by iontophoretic application of acetycholine. The other subject is concerned with the physiological and pharmacological nature of the GABA (gamma-aminobutyric acid) receptors on the primary sensory neurons. This study is aimed to clarify the ionic requirement of the GABA-mediated depolarization of the primary afferent neurons, the kinetics of GABA-GABA receptor interaction, and the interaction between GABA and antagonists. This basic information will be applied to elucidate the mechanism underlying the presynaptic inhibition in the spinal cord and higher centers.